Well logging apparatus



Oct. 3, 1950 R. P. VINCENT 2,524,150

wsu. LOGGING APPARATUS Filed Aug. :51, 1948 a ll ELECT ROMAGNETS V l2INVENTOR.

RENIC R VINCENT BY ATTORNEY Patented Oct. 3, 1950 WELL LOGGING APPARATUSRenic 1. Vincent, Tulsa, Okla., assignor to Stanclind Oil and GasCompany, Tulsa, Okla., a corporation of Delaware Application August 31,1948, Serial No. 47,068

4 Claims.

1 This invention pertains to an improvement in well logging instruments.More particularly, this invention relates to a null type instrument for.

making a substantially continuous log of a well wherein variations in awell characteristic unbalance a balanced electric circuit and the ad-Justment required to rebalance the circuit is recorded as a function ofthe well characteristic.

In my copendlng joint application S. N. 723,480, filed January 22, 1947,a measuring instrument for wells was disclosed. In that application anautomatic means for balancing an electrical circuit such as a Wheatstonebridge or a potentiometer was disclosed. The measuring instrumentdescribed in the previous joint application was, however, limited to anintermittent balancing and recording device. In many instances asubstantially continuously recording automatic balancing circuit isdesirable.

It is therefore an object of this invention to provide an improved welllogging apparatus. A more specific object of this invention is toprovide an improved well logging instrument of the type employing abalancing circuit wherein a well characteristic is indicated by thunbalance in said circuit. A further object of this invention is toprovide an improved apparatus for indicating variations in the fluidvelocity in a well. A still further and more specific object of thisinvention is to provide a well logging instrument in which an element ofa balancing circuit is varied by a well characteristic, the circuit isrebalanced in the Well, and the adjustment necessary to rebalance thecircuit is recorded as an indication of variations in a Wellcharacteristic. These objects will become manifest and additionalobjects will be apparent as the description of the invention proceeds.In this description, ref erence will be made to the accompanyingschematic diagram of a preferred embodiment of my invention.

Referring to this drawing, the well logging instrument consistsessentially of an outer case III, which is adapted to protect theworking elements from contamination by well fluids as well as fromexposure to the high pressures encountered in a deep well, a frameworkll, mounted in the outer case l0, and detecting and recording elementssupported in said framework. An opening I2 in the lower end of case Iand outlet ports l3 in the side walls of the case provide a means bywhich circulation of fluids through the lower compartment ll of thinstrument may be established. In the preferred embodiment of thisinvention the instrument is adapted to measurlng fluid velocities inwells. In such an embodiment the sensitive elements of a balancingcircuit; for example, two resistances l5 and 16 of a Wheatstone bridgecircuit are disposed within the compartment ll of the instrument and inthe fluid flow stream. These resistances are preferably made from amaterial such as platinum having a high temperature coefficient ofresistance.

It is generally desirable to compensate the balancing circuit fortemperature changes within the well. This may be accomplished by, forexample, selecting a resistance It having a substantially greaterdiameter than resistance !5, equal total resistances being provided bythe increased length of resistance it with respect to resistance l5.Thus, the radiation area of resistance 56 being substantially greaterthan the area of resistance l5, when resistances l5 and I6 are energizedby a battery El, the temperature of resistance i 5 is substantiallyhigher than the temperature of resistance is and of the well fluidssurrounding the instrument. This resistance 15, being hotter than thewell fluids, is sensitive to the velocity of the well fluidsthe higherthe velocity the greater the heat loss and accordingly the lower theresistance. The other arms l8-and E9 of the Wheatstone bridge which arepreferably made of a temperature insensitive material such as manganin,are connected at the bridge terminal 2i through a measuring instrumentsuch as a galvanometer 22 to the slider of a variable resistance 23,this variable resistance being disposed between resistances I5 and I6 asindicated. It will thus be apparent that as the velocity of a fluidthrough the compartment it varies, the conductivity of resistance l5varies and such variations will tend to unbalance. a previously balancedbridge thus deflecting the armature 2 of galvanometer 22.

As the galvanometer armature 24 is deflected, the associated indicator25 will be deflected to the right or left about the axis 26 of thearmature. A conducting element, hereinafter referred to as a pole 2'! cla reversing switch 28, is connected to the indicator 25 or thegalvanometer. When the bridge is unbalanced, pole 2 1 is moved either tothe right or the left depending upon the direction of unbalance of thebridge. As the pole is moved to the right, for example, as it might bewith a fluid velocity above a predetermined average velocity at whichthe bridge is balanced, the pole is disposed between right anvil 29 andhammer 30. This right anvil 29 and hammer 30 are electrical conductingelements. Hammer 30 3 is reciprocated by motor II which is driven bybattery 82 through a jack shaft 33, bevel sears 24, crank 35, and rod35. Motor 3| also rotates two solenoids 2'! and II via Jack shaft 32.Solenoid 31 is rotated by direct drive between gear 39 on the solenoidand pinion 40 on jack shaft 22. Solenoid 38 is rotated in an oppositedirection to solenoid 21 by interposing a set of idler gears 42 betweenpinion 42 on jack shaft 33 and gear 44 on the solenoid. With pole 21disposed between right anvil 25 and hammer 30, as hammer III isintermittently pressed down a circuit is completed through hammer-3|,pole 21, and anvil 28. Battery 32 will thereupon energize solenoid 51.As this solenoid is energized, clutch plate 45 is urged downwardlyagainst the face of the electromagnet and thus tends to rotate withelectromagnet 31. A pin 45 in shaft 41 is disposed in a longitudinalslot 48 of clutch plate 45. This longitudinal slot restricts relativerotation but permits longitudinal motion between the clutch plate 45 andshaft 41. Therefore, clutch plate 45 being attracted to electromagnet31, the shaft 41 is rotated in the same direction. Shaft 41 is providedwith threads 49 and a nut Nut 50 is preferably made of insulatingmaterial such as any of the phenol-formaldehyde type resins or the like.A slider or brush 5| is connected to nut 50 and rides upon variableresistor 23. A stylus 52 is also connected to nut 50 and is adapted toindicate or record on a chart 53 the position of the nut relative to theinstrument. Chart 53 is preferably mounted on a cylinder 54 which may berotated through shaft 55 by a clock or other substantially constantspeed means (not shown). The rotation of shaft 41 is thus preferablydriven by motor 3| through reduction gears and reversing clutches but insome cases a reversing motor or 2 motors driven in opposite directionsdirectly or indirectly connected with shaft 41 can be adapted to drivenut 50, hammer 3|! being driven continuously by a. separate motor.

Shaft 41 being rotated by solenoid 31 as previously described, nut 50 ismoved on threads 49. This movement of nut 50 slides the brush 5| alongvariable resistor 23. The movement of brush 5| on variable resistance 23tends to return pole 21 to the left and to a neutral position. As thepole reaches a neutral position between right anvil 28 and left anvil56, the circuit through hammer 30 and right anvil 29 is broken andtherefore solenoid 31 is de-energized. The stylus 52 therefore indicateson chart 53 the position of brush 5| relative to variable resistance 23in which the indicator 25 is in a null position and the bridge isbalanced. Furthermore, the stylus indicates the velocity of fluid,either gaseous or liquid, past the velocity sensitive resistance l5.

As the velocity of fluid through chamber l4 and past resistance I5 isvaried in an opposite direction by, for example, a decrease in fluidvelocity below a predetermined average velocity at which the bridge isbalanced, the Wheatstone bridge is unbalanced likewise in an oppositedirection and the indicator 25 may accordingly be shifted to a positionat the left. In such a position, pole 21 is disposed between hammer 35and left anvil 55. closing a circuit through the switch to the uppersolenoid 25 as hammer 30 is periodically depressed. As this solenoid isthus energized, clutch plate 45 is attracted to the lower face of thesolenoid and by the friction between the solenoid face and the clutchplate, shaft 41 is driven with solenoid 25. Since solenoid 28 is turningin an opposite direction from solenoid 21, the direction of rotation ofshaft 41 is opposite to it direction of rotation when clutch plate 45 isattracted by solenoid I1. Nut 54 and brush II are therefore moved in anopposite direction. This movement of bl'llh 5| relative to variableresistor 22 tends, as previously described; to balance the bridgecircuit and indicator 25 and pole 21 are again placed in a neutralposition between right anvil 25 and left anvil 55.

It is sometimes desirable, in order to prevent an overload on motor II,that a limiting switch 51 be incorporated in the control circuits forthe positioning of nut 55 and brush II. This limiting switch may consistof, for example. an upper flexible contact 54, a lower flexible contact55 and a central flexible pole 5|. Normally, there is a closed circuitthrough upper flexible contact 55, the central flexible pole 5|. and thlower flexible contact 52. However, as nut 50 is raised, th nut liftscentral flexible pole 5| by a rod 52 which has an upset head 52,breaking the electrical circuit between lower contact 59 and the centralflexible pole 5| thus, even though the bridge is unbalanced and pole 21is disposed between left anvil 54 and hammer III, the motion of nut 54is stopped and cannot be moved except by an unbalance oi the bridge inan opposite direction whereby solenoid 21 is energized. The movement ofnut 55 in a downward direction is also limited in the same manner whenthe nut strikes the lower upset 54 and breaks the circuit between upperflexible contact 55 and the central flexible pole 5|.

In operation, a chart having markers for time correlation is placed incylinder 54. Rotation of the cylinder is commenced by, for example,starting a clock. The variable impedance elements in the bridge are thenadjusted so that the bridge will be balanced at substantially an averagefluid velocity in the well. when th outer case is closed. the instrumentis lowered into the well on a cable which is attached at the upper endof the outer case ll. Since the fluid produced by any well may bedifl'erent from other wells, it is generally duirable, prior to making asurvey of the fluid velocity in any well, particularly a producing wellas distinguished from an input well. to calibrate the instrument for theparticular fluid produced by that well. The instrument may be calibratedby locating it at any position in a well where the diameter is known as,for example, in the tubing. The well is then produced and the productionrate recorded. From this data the operator obviously can detcrmine thefluid velocity at the position of the instrument in the well. Generally,to calibrate the instrument the well is produced at 3 or more differentproduction rates thereby providing preferably a substantial range ofvelocities encompassing the fluid velocity at the test section of thewell. Each of these calibration tests are recorded on chart II atdifferent times which may by time comparison be correlated with theactual well production and fluid velocity rates as kept at the surface.

After the flow meter is calibrated it is lowered to a position in thewell where the actual fluid velocity is unknown; as for example, betweentwo producing horizons. The well is then produced at a known rate for areasonable length of time; for example, between about 5 and about 30minutes so that the record produced by the stylus is long enough to bedistinguished from other records on the chart. Obviously, any number ofproduction tats may be made at several positions in the well and eachproduction test may be distinguished from the others by time correlationwith production tests at the surface. Sometimes it may be desirable,particularly where a fluid velocity test is made in an uncased hole, toconsider hole diameter in the determination of fluid velocities andrelative production rates or permeability profiles within the well. Awell caliper survey may be made simultaneously with or independent ofthe fluid velocity survey.

Thus, I have described a preferred embodiment of my invention in theterms of a fluid velocity metering apparatus. Obviously, the wellsensitive impedance may be varied by any other well characteristic. Forexample, variations in formation resistivity, radioactivity or the likemay be impressed upon this well sensitivity impedance without departingfrom the spirit of the invention. It is thus to be understood that theinvention is not to be construed as being limited to the particularembodiment described in detail. The invention is instead limited only bythe scope of the appended claims.

I claim:

1. In well logging apparatus including a chart and means to indicate onsaid chart variations in a well characteristic, an electric motorenergized from an adjacent source, two oppositely rotating electricallyactuated clutches driven by said motor, a single rotatable shaft adaptedon actuation of one of said clutches to drive the indicating meanslinearly, electrical means including at least one impedance responsiveto a condition in said well for selectively actuating said clutches assaid condition varies, and a cylindrical watertight case adapted to belowered into a well enclosing all of said apparatus except said at leastone impedance.

2. In well logging apparatus including a chart and a recording stylus toindicate on said chart variations in a well characteristic, an electricmotor energized from an adjacent source, two oppositely rotatingelectrically actuated clutches driven by said motor, a single rotatableshaft adapted on actuation of one of said clutches to drive linearlysaid recording stylus, a bridge circuit including a well-sensitiveimpedance responsive to variations in a condition in said well, saidcircuit including an adjustable balancing impedance coupled to saidstylus, an indicator responsive to unbalance of said bridge due tovariations in said condition, means periodically actuated by said motorand responsive to the position of said indicator for selectivelyactuating one of said clutches, and a cylindrical watertight caseadapted to be lowered into a well and enclosing all of said apparatusexcept said wellsensitlve impedance.

3. An apparatus for continuously recording in a well the fluidvelocityat a point in said well comprising a Wheatstone bridge having two armsin the fluid stream, both arms having substantially equal totalresistance but having unequal cross-sectional areas to compensate forchanges in temperature of said fluid stream, a variable resistance insaid wheatstone bridge, a brush in contact with said variableresistance, a galvanometer in a diagonal of said bridge circuit, anindicator arm on the armature of said galvanometer, a switch pole onsaid indicator arm, a right anvil and a left anvil both of said anvilsbeing conductors and having a space therebetween, a motor, a hammerreciprocated by said motor, said switch pole, anvils and hammer coactingperiodically to close a circuit through said hammer, said pole and oneof said anvils when said bridge is unbalanced, two electromagnets drivenin opposite directions on a threaded shaft by said motor, a clutch platedisposed on said shaft between said electromagnets, said clutch platebeing keyed to rotate with said shaft but free to move axially alongsaid shaft and contact independently the faces of said twoelectromagnets, a not on said shaft, said brush being affixed to saidnut, one of said electromagnets being energized and rotating said clutchplate and said shaft in one direction when said bridge is unbalanced inone direction and said'circuit through said hammer, pole and one of saidanvilsv is closed, the other of said electromagnets being energized androtating said clutch and said shaft in the opposite direction when saidbridge is unbalanced in the opposite direction and said circuit throughsaid hammer, pole ,and the other of said anvils is closed, whereby themovement of said nut and said brush responds to the unbalance in saidbridge and rebalances said bridge and whereby the movement of said nutis indicative of variations in said fluid velocity.

4. An apparatus according to claim 3 in which each of saidelectromagnets is de-energized as said not approaches the limit of itstravel resulting from energizing such electromagnet.

RENIC P. VINCENT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 22,637 Keinath Aug. 24, 19451,022,498 Northrup Apr. 9, 1912 1,691,600 Brush, Jr., et a1. Nov. 13,1928 2,425,733 Gllle et a1 Aug. 19, 1947 FOREIGN PATENTS Number CountryDate 18.563 Great Britain 1914

